Merge branch 'bugfix/SQL-updates' into develop

Fixed a couple of bugs in the SQL scripts discovered as part of final integration testing.

- Updated migration script to ensure that the `BaseTopic` attribute was correctly renamed. Previously, there were two errors in the migration script which prevented this from being correctly updated (0929fb4).
- Updated the `CreateTopic` stored procedure so that it will correctly create a root topic if none already exists (ade1f90). This resolves a bug introduced previously when allowing _additional_ root topics to be added (5000ca0); in doing so, I inadvertently prevented the _initial_ root topic from being created.

Author: JeremyCaney

OnTopic.Data.Sql.Database/Scripts/Upgrade from OnTopic 4 to OnTopic 5.sql

@@ -133,8 +133,8 @@ WHERE	ReferenceKey		= 'Topic'
 
 UPDATE	Topics
 SET	TopicKey		= 'BaseTopic'
-WHERE	TopicKey		= 'DerivedTopic'
-AND	ContentType		= 'TopicReferenceAttributeDescriptor'
+WHERE	TopicKey		= 'InheritedTopic'
+AND	ContentType		= 'TopicReferenceAttribute'
 
 --------------------------------------------------------------------------------------------------------------------------------
 -- MIGRATE ATTRIBUTE KEYS

OnTopic.Data.Sql.Database/Stored Procedures/CreateTopic.sql

@@ -90,7 +90,7 @@ IF (@ParentID IS NOT NULL)
   END
 ELSE
   BEGIN
-    SELECT	@RangeRight		= MAX(RangeRight) + 1
+    SELECT	@RangeRight		= ISNULL(MAX(RangeRight), 0) + 1
     FROM	Topics
     WITH (	TABLOCK
     )